Wetting up farmland for biodiversity

Field drainage and removal of field ponds over recent decades has reduced the amount of wet habitat available to farmland wildlife for drinking and foraging.   Future climate change and increasing human demands on water may accelerate this trend. 

Wetting Up Farmland for Biodiversity is a Defra-funded research project which explores the opportunities for, and benefits of, recreating wet habitats on farmland without impinging on the cropped area. The project is a collaboration with the RSPB and Ponds Conservation Trust.

Although other wet habitats are considered, the main focus of the project is on two types of feature:

• Bunded ditches
  These are simply small dams across ditches to allow water to back up, retaining water in the ditch in the summer than would otherwise be the case.
• Paired Ponds
  Water is diverted from an adjacent ditch into a pair of field corner ponds which are separated by a grass bund.

These features are intended to provide a source of invertebrate food for birds, as well as water for drinking, and to benefit aquatic invertebrates in their own right.  They may also contribute to mitigation of diffuse pollution through sedimentation and consequent removal of phosphorus  from the watercourse. 

Our findings reveal that birds make significantly more use of bunded ditches and paired ponds than the control plots, especially in the summer, although the number of birds involved was never high.  Emergent insect biomass was also significantly higher in bunded ditches than in control plots and was associated mainly with areas of bare wet mud (left by receding water) and lower levels of hedgerow shading.  Bird visit rates to our wet features were positively correlated with insect biomass, suggesting that birds actively seek out areas where foraging will be most productive. 

Both birds and their invertebrate prey therefore appear to benefit from the creation of small field boundary wetlands.  However, our experience suggests that such features could be improved to provide greater conservation benefit while minimising the impact on the cropped area.